1. Field of the Invention
The invention concerns a rotor blade of a wind power installation, and a wind power installation. As state of the art in this respect attention should be directed generally to the book ‘Windkraftanlagen’, Erich Hau, 1996. That book contains some examples of wind power installations, rotor blades of such wind power installations as well as cross-sections of such rotor blades from the state of the art. Page 102, FIG. 5.34, illustrates the geometrical profile parameters of aerodynamic profiles in accordance with NACA. It is to be seen in that respect that the rotor blade is described by a profile depth which corresponds to the length of the chord, a greatest camber (or camber ratio) as the maximum rise of a median line over the chord, a camber reserve, that is to say the location with respect to the profile depth where the greatest camber is provided within the cross-section of the rotor blade, a greatest profile thickness as the largest diameter of an inscribed circle with the center point on the median line and the thickness reserve, that is to say the location with respect to the profile depth where the cross-section of the rotor blade assumes its greatest profile thickness. In addition the leading-edge radius and the profile co-ordinates of the underside and the top side are brought into consideration to describe the cross-section of the rotor blade. The nomenclature known from the Erich Hau book is to be retained inter alia for the further description of the cross-section of a rotor for the present application.
2. Description of the Related Art
Rotor blades are to be optimized in regard to a large number of aspects. On the one hand they should be quiet while on the other hand they should also afford a maximum dynamic power so that, even with a quite slight wind, the wind power installation begins to run and the nominal wind speed, that is to say the speed at which the nominal power of the wind power installation is also reached for the first time, is already reached at wind strengths which are as low as possible.
If then the wind speed rises further, nowadays when considering pitch-regulated wind power installations the rotor blade is increasingly set into the wind so that the nominal power is still maintained, but the operative surface area of the rotor blade in relation to the wind decreases in order thereby to protect the entire wind power installation or parts thereof from mechanical damage. It is crucial however that great significance is attributed to the aerodynamic properties of the rotor blade profiles of the rotor blade of a wind power installation.